Hmm, this is far less obscure than some of the other comments, but very much indie at the same time:

Enderal

This is technically a mod, but is in Steam as its own game (vs in the Steam Workshop) bc it's a legit full game; they broke Sktrim down to its assets and rebuilt a completely new game out of it. So, familiar mechanics and engine; brand new everything else (lore, terrain, voice acting, music, etc).

It's a passion project from an indie dev crew iirc based in Germany, called SureAI - note that they've been around since 2003, and have no connection to the the slop we're calling "AI" nowadays.

Enderal is a 90-10 slit of absolute masterpiece and absolute jank - it's Skyrim's engine, so it has all of Skyrim's problems. You WILL run into stupid shit like quest items falling through the floor, so save frequently (real save, that makes backups, not just quick) and don't be afraid to fix shit with console commands; but once you get past the Skyrim jank, you'll be treated with an absolutely incredible story that delves into philosophical and emotional topics. You know that sunken feeling you get when you finish a really good book cuz you CRAVE more, but know it's over? Enderal is the only videogame that's ever evoked that from me. Cannot overstate how damn good the writing is!

Actually playing it... it's been a while, so it might be different now, but last I played it required you to have either the original release or special edition version of Skyrim already in your Steam Library, enabling it to hijack the assets. So, whichever one you have, download the corresponding version of Enderal. The plus side is that it's completely free barring the Skyrim requirement - and like, actual free, with no ads or micros or any of that BS.

https://store.steampowered.com/app/933480/Enderal_Forgotten_Stories/

https://store.steampowered.com/app/976620/Enderal_Forgotten_Stories_Special_Edition/

If you have both, DL the version that you don't usually play in Skyrim - this will enable you to have both installed at the same time if desired, with no fuckery from competing file use. ...if just one version, back up your Skyrim saves before installing, as it's been known to cause issues.

Anyway, remember that first playthrough of Skyrim when everything was brand new and you didn't know the game like the back of your hand? ...this is the closest you'll get to revisiting that experience. Possibly surpassing, since Skyrim's story is kinda cliche; Enderal will make you feel something new.

One pseudo spoiler: they redid combat and leveling mechanics. Don't lean too heavily on the tricks you know from Skyrim. Aka, sneaky archer will get your ass handed to you. Experiment with the different combat options! Avoid additional spoilers like the plague.